[TRNSYS-users] From global solar radiation to direct and diffuse SR

Thu Jun 17 07:53:34 PDT 2021

Wirich,

Type 546 in the Solar Library from TESS estimates the direct and diffuse
components from the global radiation on a tilted surface. You could possibly
use one Type 546 for each of your orientations, to calculate the
diffuse/direct split from the measured total radiation. Of course there is
no guarantee the different estimates would be consistent, so for example the
horizontal radiation you will get from the different Type 546 units will
probably be different, but at least you would use your global radiation
measurements on all orientations.

Michaël Kummert

Polytechnique Montréal

From: David BRADLEY via TRNSYS-users <trnsys-users at lists.onebuilding.org> 
Sent: June 17, 2021 10:18
To: Freppel, Wirich <Wirich.Freppel at saint-gobain.com>; TRNSYS users mailing
list at OneBuilding.org <trnsys-users at lists.onebuilding.org>
Cc: David BRADLEY <d.bradley at tess-inc.com>
Subject: Re: [TRNSYS-users] From global solar radiation to direct and
diffuse SR

Wirich,

 Unfortunately Type16 can't convert from an arbitrary angle back to
horizontal then do its calculations. I remember seeing (perhaps even using)
such a component a few thousand years ago but would not know where to put my
hands on it again.

 I would think that with such a slight slope as 10° you could use sines and
cosines to determine what the global on the horizontal actually was before
feeding it to Type16.

best,

 David

On 06/17/2021 08:38, Freppel, Wirich wrote:

Hello David, 

That is an excellent idea !

I did not exactly measure horizontal radiation since the “horizontal”
pyranometer was placed on the roof, which is 10° tilted. I guess I could try
first by considering the roof as horizontal since 10° is not that much. I
could also estimate the horizontal radiation by calculation, or finally,
does the type 16 can do this job ? If I understand, Type 16 can go from
horizontal to any tilt but not the other way around, does it ?

Thanks for your help

Wirich FREPPEL
Development engineer 

COSMOS - Buildings Energy Performance & Daylighting Group

Cell: +33 637 053 174

Saint-Gobain Research Compiègne

De : David BRADLEY  <mailto:d.bradley at tess-inc.com> <d.bradley at tess-inc.com>

Envoyé : jeudi 17 juin 2021 15:21
À : TRNSYS users mailing list at OneBuilding.org
<mailto:trnsys-users at lists.onebuilding.org>
<trnsys-users at lists.onebuilding.org>
Cc : Freppel, Wirich  <mailto:Wirich.Freppel at saint-gobain.com>
<Wirich.Freppel at saint-gobain.com>
Objet : Re: [TRNSYS-users] From global solar radiation to direct and diffuse
SR

Wirich,

 Did you also by chance measure global on the horizontal? If so then what I
would suggest you do is to define your same vertical surfaces in Type16 and
then run your measured global horizontal through it. Type16 will give you an
estimate of how the global breaks up into beam and diffuse not only for the
horizontal but also for the vertical surfaces. I would then compute the
ratios of beam to global and diffuse to global that Type16 gives you for
each surface and then use those ratios multiplied by your actual
measurements to come up with the components that Type56 wants. 

kind regards,

 david

On 06/17/2021 04:15, Freppel, Wirich via TRNSYS-users wrote:

Dear Trnsys users,

I measured global solar radiation on vertical surfaces (one for each
orientation) using a pyranometer. I would like to use these data on my
building model instead of using “internal calculation”.

Type 56 asks for direct and diffuse solar radiation arriving on the surface.
How can I manage the data to send the appropriate values to Type 56 ?

Thanks in advance for your help

Wirich FREPPEL
Development engineer 

COSMOS - Buildings Energy Performance & Daylighting Group

Cell: +33 637 053 174

Saint-Gobain Research Compiègne

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David BRADLEY
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Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI  53703 USA

P:+1.608.274.2577
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